1. Field of the Invention
The present invention relates to an inkjet recording apparatus, and more particularly to color correction technology that can be suitably applied to an inkjet recording apparatus forming an image by using a treatment liquid insolubilizing or aggregating coloring material of ink and a plurality of color inks.
2. Description of the Related Art
An inkjet recording apparatus that carries out color printing forms color images on a recording medium by ejecting cyan (C), magenta (M), yellow (Y), black (K), or other color inks from nozzles of a recording head, so that the ejected inks adheres to the recording medium.
Japanese Patent Application Publication No. 2004-112470 proposes a function for correcting the color displacement caused by changes in the color reproduction characteristics due to individual differences in the output device that is used in printing or in the operating environment. In this function, a predetermined standard color image is output at a predetermined number of repetitions, and by reading this color image with a sensor, calibration is automatically carried out not only for gray balance (color displacement of the primary color), but also for the higher order colors (secondary color, tertiary color) obtained by combining a plurality of ink colors.
Also, Japanese Patent Application Publication No. 2005-212246 discloses the constitution of a printing device that selects a color conversion process in accordance with environmental conditions detected by temperature and humidity sensors. The color conversion process uses a color conversion process table in accordance with the environmental conditions that affect printing (temperature, humidity), in order to reduce the variation in the printing results due to changes in the environmental conditions, such as temperature, humidity, and so on.
Also, recently, in order to solve problems such as deposition interference (merging of adjacent dots) in high speed inkjet printing, two liquid reaction technology has been proposed in which treatment liquid that aggregates the ink color material is applied or deposited prior to deposition of the ink.
However, in an image forming apparatus that forms images by inkjets on a sheet to which treatment liquid was applied, in a case where the next ink (the secondary color) is deposited after an image is formed in the first color (the primary color) by depositing the first color, the aggregation action of the treatment liquid is different from that of the first color. As a result, there is a variation in the color density created by the second color (the secondary color). Likewise for the third color (the tertiary color), and the fourth color (quaternary color), so there is an image forming problem that the effect of the treatment liquid changes for each ink color.
Examining this phenomenon, it is found that when depositing superimposed a plurality of ink dots by inkjets onto a sheet on which treatment liquid has been applied, sufficient treatment liquid is supplied for the dot deposited from a preceding nozzle. However, insufficient treatment liquid is supplied for the dots deposited from the subsequent nozzles. Therefore, the dot size of the preceding dot is made smaller by the sufficient aggregation action of the treatment liquid. However, aggregation of the subsequent dots is insufficient, so the dot sizes become larger.
When the colors of the ink ejected from the preceding nozzle and the ink ejected from the subsequent nozzle is different, for example when the ink from the preceding nozzle is magenta (M) and the ink from the subsequent nozzle is black (K), the preceding deposition (M) is sufficiently aggregated by the treatment liquid, so the dot size is always small. However, the treatment liquid is consumed by the magenta (M) which was deposited first, so the subsequently deposited black (K) has insufficient aggregation. Therefore, the dot size of the subsequently deposited black (K) is larger compared with the case that the single color black (K) only is deposited.
As described above, when the dot size varies due to differences in the aggregation effect, the color and color hue vary, so that it is difficult to obtain a desired image.